JP3795785B2 - Multistage telescopic arm hydraulic circuit - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a hydraulic circuit of a multistage telescopic arm that drives a telescopic arm including a clamshell bucket and a telescopic clamshell working machine.
[0002]
[Prior art]
Conventionally, a telescopic clamshell is known as a deep excavator for infrastructure construction such as steel tower foundation work and water and sewage, gas and telephone. The telescopic clamshell includes a telescopic arm that can be expanded and contracted on a boom of a hydraulic excavator, and further includes a clamshell bucket that can be opened and closed at the tip thereof. The telescopic arm is extended, the clamshell bucket is opened, and it is pushed against the ground to scoop up the soil and excavate.
[0003]
The telescopic arm has a multi-stage arm such as an outer arm and an inner arm. The outer arm is swingably attached to the boom, and the inner arm is accommodated in the outer arm so as to be able to appear and retract, and is a multi-stage multi-stage telescopic arm. Is configured. Then, by extending the inner arm from the outer arm, the telescopic arm is extended, the clamshell bucket is inserted into the vertical hole, the inside of the vertical hole is excavated, the inner arm is accommodated in the outer arm, the telescopic arm is contracted, Pull the clamshell bucket loaded with to the ground.
[0004]
The telescopic clamshell can extend and contract the telescopic arm perpendicularly to the ground, so that it can work in narrow spaces such as between structures. In addition, because of its high work efficiency, there are many opportunities for use in the foundation work of structures and subway works in urban areas. However, especially when working in urban areas, it is important to perform construction in a short period of time, and an improvement in the amount of work is required.
[0005]
[Problems to be solved by the invention]
However, if a telescopic arm with a large excavation depth or a bucket with a large capacity is used to improve the work volume of the telescopic clamshell, the weight increases, the stability of the construction machine itself decreases, and the telescopic arm expands and contracts. Therefore, there is a problem that the life of the wire rope used together with the hydraulic cylinder is reduced. In addition, the pump flow rate decreases due to an increase in cylinder holding pressure due to the use of a large bucket, and sufficient arm expansion / contraction speed cannot be obtained.
[0006]
An object of the present invention is to provide a hydraulic circuit for a telescopic clamshell multistage telescopic arm and a telescopic clamshell working machine capable of improving the amount of work by increasing the telescopic speed of the arm.
[0007]
[Means for Solving the Problems]
  A hydraulic circuit for a multistage telescopic arm according to the present invention is driven by pressure oil discharged from a hydraulic pump, and communicates a hydraulic cylinder that expands and contracts the multistage telescopic arm of a telescopic clamshell, a rod chamber of the hydraulic cylinder, and a hydraulic pump. A first check valve provided in the rod-side pipe line, which allows pressure oil discharged from the hydraulic pump to flow into the rod chamber and prohibits pressure oil from the rod chamber from flowing out to the hydraulic pump side; A short circuit connecting the rod chamber of the hydraulic cylinder and the bottom chamber via a counter balance valve, the rod chamber side inlet of the short circuit being between the rod chamber and the first check valve And the counter balance valve is opened at least according to the pilot pressure from the rod chamber side.The And a second check valve that allows the flow of pressure oil from the bottom chamber to the rod chamber and prohibits the flow of pressure oil from the rod chamber to the bottom chamber. The above object is achieved by connecting to the rod side pipe line between the rod side port and the first check valve.
[0008]
The counter balance valve is desirably opened according to the pilot pressure from the rod chamber side and the bottom chamber side. A pilot line for supplying pilot pressure oil acting in a direction to close the counter balance valve when the hydraulic cylinder is contracted to the counter balance valve is further provided, and the inlet of the pilot line is connected to the hydraulic pump side rod from the first check valve. You may provide in a side pipe line.
[0009]
FirstThe second check valve may be incorporated in the counter balance valve.
[0010]
Rod side branch pipe extending from the rod side pipe line to communicate the rod chamber of the hydraulic cylinder and the tank, bottom side additional pipe line for communicating the bottom chamber of the hydraulic cylinder with the tank, and the rod side You may further provide the direction switching valve which switches so that either a branch pipe line or a bottom side additional pipe line may be connected with a tank. The directional switching valve communicates the rod side branch line with the tank when the hydraulic cylinder is extended and stopped, shuts off the bottom side additional line from the tank, and when the hydraulic cylinder contracts, the bottom side additional line is connected to the tank. It is desirable to communicate and block the rod side branch pipe from the tank.
[0011]
Further, a sequence valve may be provided in the short circuit on the outlet side of the counter balance valve.
[0012]
  A telescopic clamshell working machine according to the present invention has a multistage telescopic arm attached to a boom provided on a telescopic clamshell working machine body, and a clamshell bucket attached to the tip of the multistage telescopic arm. Claims 1 to6The above-mentioned object is achieved by controlling with the hydraulic circuit of the multistage telescopic arm described in any of the above.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an overall view of a hydraulic excavator equipped with a hydraulic circuit of a multistage telescopic arm according to the present invention. FIG. 2 is a side view of a multistage telescopic arm according to an embodiment of the present invention.
[0014]
As shown in FIGS. 1 and 2, the excavator includes a lower traveling body 101, an upper swinging body 102 that is pivotably connected to an upper portion of the lower traveling body 101, and a boom cylinder 110C. A boom 110 that is movably attached, a multistage telescopic arm 120 that is swingably attached to the tip of the boom 110 by an arm cylinder 120C, and that is telescopically driven by a hydraulic cylinder and a wire rope, which will be described later, and a multistage telescopic arm 120 The clamshell bucket 140 is attached to the tip and is driven to open and close by a hydraulic device 141 to perform excavation work. The upper swing body 102 is provided with a cab 103, a machine room 104 that houses an engine, a hydraulic source (not shown), a counterweight 105, and the like.
[0015]
The multistage telescopic arm 120 is a three-stage telescopic arm including an outer arm 120o, a second arm 120s, and an inner arm 120i. The inner arm 120i is inserted in the second arm 120s, and the second arm 120s is inserted in the outer arm 120o so as to be extendable. A clamshell bucket 140 that can be opened and closed via a pin 131 is attached to a pair of brackets 130 attached to the tips of the inner arms 120i. The outer arm 120 o includes a pair of brackets 132 on the side facing the boom 110. The telescopic arm 120 is swingably attached to the boom 110 by inserting the pin 133 into the bracket 132.
[0016]
In the hydraulic cylinder 40 for arm extension / contraction provided in the inner arm 120i, the cylinder tube is supported by the inner arm 120i, and the tip end portion of the cylinder rod is supported by the second arm 120s. The telescopic arm 120 has two support ropes 121 and two push ropes 123 each.
[0017]
The support rope 121 is connected to one end of the outer arm 120o via the equalizer device 125, and is connected to the upper end of the inner arm 120i via a lifting sheave 122 attached to the lower end portion of the second arm 120s. The support rope 121 sends out and pulls up the second arm 120 s according to the expansion and contraction operation of the arm expansion cylinder 40. The pushing rope 123 is connected to one end of the outer arm 120o, and is connected to the upper end of the inner arm 120i via a pushing sheave 124 attached to the upper end portion of the second arm 120s. When the arm expansion / contraction hydraulic cylinder 40 is extended, the push rope 123 is pulled in accordance with the operation of the inner arm 120i, so that the second arm 120s is pushed through the push sheave 124. Thereby, the pushing force of the telescopic arm 120 when pressing the clamshell bucket 140 against the ground can be obtained.
[0018]
As described above, the telescopic clamshell working machine in which the clamshell bucket 140 is attached to the telescopic arm 120 according to the present embodiment is a telescopic arm using the arm expansion / contraction hydraulic cylinder 40 and the wire ropes 121 and 123 in combination. 120 is expanded and contracted.
[0019]
The telescopic clamshell has mainly four work modes as follows.
(1) Load holding: At the time of arm alignment or fine adjustment, the arm is stopped at an arbitrary position to fix the bucket position, and the load (extension cylinder 40, second arm 120s, inner arm 120i, and clamshell bucket 140 Hold its own weight).
(2) Normal expansion / contraction: When the clamshell bucket is empty, the arm is inserted into the vertical hole and extended. After scooping earth and sand into the clamshell bucket, retract the arm and pull up the bucket.
(3) Excavation: After extending the arm, open the clamshell bucket and press the clamshell bucket against the ground by the arm telescopic cylinder force, and scoop up a sufficient amount of earth and sand into the bucket. In addition to pressing by arm telescopic cylinder force, pressing by jackup by boom cylinder force can also be performed.
(4) Pulling out: After excavation, the clamshell bucket may stick to the ground. In this case, the clamshell bucket is pulled away from the ground by the arm telescopic cylinder force or the boom cylinder force, and then lifted.
[0020]
FIG. 3 shows a hydraulic circuit of a multistage telescopic arm according to an embodiment of the present invention. As shown in FIG. 3, a hydraulic circuit for a telescopic arm according to the present invention includes a variable displacement main pump 10 driven by an engine (not shown) and a control valve for controlling the flow of pressure oil discharged from the main pump 10. 20, a telescopic arm expansion / contraction cylinder 40 driven by pressure oil controlled by the control valve 20, and a regeneration valve unit 30 for amplifying the telescopic arm expansion / contraction speed. Further, a directional switching valve 14 is provided which is switched by the operation of the operation pedal 21 by the operator and communicates the rod chamber 40 a or the bottom chamber 40 b of the expansion cylinder 40 with the tank 22. In order to prevent an overload state of the expansion / contraction cylinder 40, an overload relief valve 23a is provided between the control valve 20 and the expansion / contraction cylinder 40 to the branch line from the bottom side line 15 and the rod side line 16, respectively. , 23b.
[0021]
The bottom chamber 40b and the tank 22 are communicated with the ports P2 and P3 of the bottom chamber 40b of the arm telescopic cylinder 40 via the bottom piping 15 and the direction switching valve 14 for communication with the control valve 20 on the main body side. Pipe lines 13 are connected to each other. That is, two return circuits are provided for the return pressure oil from the bottom chamber to flow into the tank 22 when the telescopic cylinder 40 is contracted. Further, a contraction rod side conduit 16 communicating with the control valve 20 on the main body side is connected to the port P1 of the rod chamber 40a. When the expansion cylinder 40 is extended or stopped, pressure oil in the rod side pipe 16 (between a check valve 8 and a control valve 20 described later) is supplied to the rod side pipe 16 without passing through the control valve 20. A pipe line 12 is provided for guiding to the pipe. These pipes 12 and 13 are connected to the direction switching valve 14, and one of them is communicated with the tank 22 when the position of the direction switching valve 14 is switched by the operation of the operation pedal 21.
[0022]
The regenerative valve unit 30 is provided in series with the short circuit 31 for communicating the bottom chamber 40b of the expansion cylinder 40 and the rod chamber 40a. The regenerative valve unit 30 is opened in accordance with a predetermined pilot pressure and is opened to the pressure on the rod chamber 40a side. The counter balance valve 3 and the sequence valve 5 that flow oil to the bottom chamber 40b side, and the rod side pipe line 16 on the control valve 20 side from the inlet 33 of the short circuit 31 are provided from the control valve 20 to the rod chamber of the expansion cylinder 40. A check valve 8 that allows inflow of pressure oil to 40a and prevents the reverse, and a pipe line 32 that connects the rod side pipe line 16 and the bottom side pipe line 15 closer to the control valve 20 than the check valve 8; And an overload relief valve 9 provided in the pipe line 32.
[0023]
The counter balance valve 3 and the sequence valve 5 allow the flow of pressure oil from the bottom chamber 40b side to the rod chamber 40a side, and check valve 3b that blocks the flow of pressure oil from the rod chamber 40a side to the bottom chamber 40b side. 5b are incorporated.
[0024]
The check valve 8 allows the flow of pressure oil from the control valve 20 to the rod chamber 40a of the telescopic cylinder 40, and blocks the flow of pressure oil from the rod chamber 40a to the control valve 20. Therefore, the pressure oil discharged from the rod chamber 40 a can surely flow into the short circuit 31.
[0025]
The overload relief valve 9 causes the pressure oil to flow out to the rod side pipe line 16 when the pressure oil pressure in the bottom side pipe line 15 reaches a set pressure.
[0026]
Here, the counter balance valve 3 constituting the regeneration valve unit 30 will be described. The counter balance valve 3 holds a predetermined back pressure in the rod chamber 40a of the telescopic cylinder 40 to prevent the load from dropping (extension of the telescopic arm 120) when the arm is held (stopped). The pressure oil discharged from the rod chamber 40a is sent to the bottom chamber 40b to increase the arm extension speed.
[0027]
The counter balance valve 3 is a combined internal / external pilot counter balance valve that opens not only using the primary side pressure but also using the secondary side pressure. The counter balance valve 3 will be described with reference to FIG. 4 in which the sequence valve 5 is omitted for explanation. The counter balance valve 3 is a pilot pressure that acts on the primary side, that is, the pressure oil in the rod side pipe line 16 to open the valve. Pilot line 1 that leads as a pilot pressure line 2 that leads the pressure oil in the secondary side, that is, the bottom side line 15 as a pilot pressure acting on the valve opening, and the rod side closer to the control valve 20 than the check valve 8 The pilot pressure oil is supplied by the pilot pipe line 6 that guides the pressure oil in the pipe line 16 as a pilot pressure acting on the valve closing. Pressure receiving portion of the counter balance valve 3 to which pilot pressure oil is supplied from the pilot lines 1 and 2 (the side supplied by the pilot line 1 is the rod side and the side supplied by the pilot line 2 is the bottom side) Is larger on the bottom side than on the rod side, and when the pressure on the rod side pipe line 16 is increased, the valve can be opened with a pressure smaller than the pressure on the bottom side pipe line 15. In addition to the above-described pilot pressure, a spring force by a built-in spring acts as a force acting on the valve closing.
[0028]
Here, for example, when the pressure receiving area ratio between the rod side and the bottom side of the counter balance valve 3 is 1: 2, the rod side pressure A1 supplied by the pilot pipe line 1 and the bottom side supplied by the pilot pipe line 2 The relationship between the pressure A2 and the cracking pressure A3 of the counter balance valve 3 is set to be expressed by the following (Equation 1) and (Equation 2). The pressure receiving area ratio between the rod chamber 40a and the bottom chamber 40b of the telescopic cylinder 40 is, for example, 1: 1.98, and the load holding pressure is B.
[Expression 1]
A1 + (2 × A2) = A3 (Formula 1)
[Expression 2]
(1.98 × A1) + B = A2 (Formula 2)
From (Formula 1) and (Formula 2),
[Equation 3]
A2 = (A3-B) /3.98 (Formula 3)
[0029]
When the pressure A2 that satisfies (Equation 3) is established on the bottom chamber 40b side, the counter balance valve 3 is opened. Note that the cracking pressure of the counter balance valve 3 is set higher than the cylinder maximum load holding pressure for safety, and higher than the set pressure of the overload relief valves 23a and 23b for the following reasons.
[0030]
For example, when the expansion / contraction cylinder 40 is contracted to the most contracted length state and pressure is continuously applied to the rod side pipe line 16, the rod chamber 40a rises to the set pressure of the overload relief valve 23b. While the operation pedal 21 continues to be operated to the contraction side, the counter balance valve 3 does not open because the set pressure of the overload relief valve 23b acts on the pilot line 6 as well. However, when the operation pedal 21 is returned to the neutral state from this state, the set pressure of the overload relief valve 23b remains as a residual pressure between the rod chamber 40a of the expansion cylinder 40 and the check valve 8 due to the action of the check valve 8. On the other hand, the rod side pipe line 16 closer to the control valve 20 than the check valve 8 communicates with the tank 22 by the direction switching valve 14 to be in an atmospheric pressure state, and the pilot line 6 is also in an atmospheric pressure state. Therefore, the counter balance valve 3 must resist the residual pressure in the rod chamber 40a of the telescopic cylinder 40 only by the spring force and keep the valve closed state. If the residual pressure in the rod chamber 40a is higher than the spring force, the counter balance valve 3 opens, and the telescopic cylinder 40 extends regardless of the operation of the operation pedal 21.
[0031]
The counter balance valve 3 incorporates a check valve 3b that allows the flow of pressure oil from the bottom side to the rod side. During the pushing operation, a high pressure is generated in the bottom chamber 40b of the telescopic cylinder 40, and the buckling safety factor may be reduced. Accordingly, the check valve 3b causes the pressure oil on the bottom chamber 40b side to flow out to the rod chamber 40a side, and the bottom chamber 40b and the rod chamber 40a are made to have the same pressure, thereby preventing the buckling safety factor from being lowered. By making the bottom chamber 40b and the rod chamber 40a have the same pressure, the thrusts are canceled out, and the cylinder thrust can be suppressed when a pressure lower than the set pressure of the extension-side overload relief valve 9 is generated.
[0032]
Next, the operation of the hydraulic circuit of the multistage telescopic arm according to the embodiment of the present invention will be described according to the work mode.
(1) When holding the arm
Since there is no operation of the operation pedal 21 by the operator, the control valve 20 remains in the neutral position, and the flow of pressure oil from the control valve 20 side to the telescopic cylinder side is prevented.
Due to the dead weight of the telescopic cylinder 40, the second arm 120s, the inner arm 120i, and the clamshell bucket 140, a force in the direction of extending the cylinder acts on the telescopic cylinder 40. However, the cracking pressure A3 of the counter balance valve 3 is set to be equal to or higher than the cylinder maximum load holding pressure and does not open, and there is no flow of pressure oil from the rod chamber 40a to the bottom chamber 40b. Furthermore, the check valve 8 prevents pressure oil from flowing from the rod chamber 40a to the control valve 20 side. Therefore, the telescopic arm 120 and the clamshell bucket 140 can be reliably held at arbitrary positions.
[0033]
(2) When the arm is extended
When the operation pedal 21 is operated to the arm extension side by the operator, the control valve 20 is switched to the position (a), and the pressure oil of the main pump 10 passes through the bottom side pipe line 15 for extension and the bottom of the telescopic cylinder 40. It is supplied to the chamber 40b.
The pressure oil from the main pump 10 is also guided to the pilot line 2 through the bottom side line 15. Further, the pressure on the bottom chamber 40 b also increases the pressure on the rod chamber 40 a side, and the pressure oil is guided to the short-circuit line 31 and the pilot line 1. When the above-described relationship of (Equation 3) is satisfied, the counter balance valve 3 is opened. Then, the sequence valve 5 set lower than the set pressure of the counter balance valve 3 is opened. As a result, the pressure oil discharged from the rod chamber 40a of the telescopic cylinder 40 flows into the bottom chamber 40b through the short-circuit line 31 and increases the cylinder extension speed.
[0034]
Here, since the operation pedal 21 is operated to the extension side, the direction switching valve 14 is in the position (a) by the spring force. The pipe line 12 communicates with the tank 22 and allows the pressure oil in the rod side pipe line 16 on the control valve 20 side to flow out of the check valve 8 into the tank 22. For this reason, the pressure of the pilot pressure oil guided to the pilot pipe line 6 is lowered, and only the spring force acts in the direction of closing the counter balance valve 3. As a result, the counter balance valve 3 is easily opened.
[0035]
If the sensitivity of the counter balance valve 3 is too good, even a slight pressure fluctuation may open and close and cause hunting. Therefore, by attaching the sequence valve 5, the sequence valve 5 functions as a throttle and prevents hunting. Further, hunting that occurs at the initial stage of cylinder extension is reduced by providing a throttle 4 in the pilot line 2 to slow the rising speed of the pilot pressure, thereby slowing the opening speed of the counter balance valve 3.
[0036]
(3) When the arm is pushed
As the telescopic arm 120 is extended, the tip of the clamshell bucket 140 contacts the ground. If the operator continues to operate the operation pedal 21 to the extension side or pushes down the boom 110 in order to push the bucket 140 into the ground, the pressure in the bottom chamber 40b may further increase and cause the cylinder to buckle. .
[0037]
Therefore, when the clamshell bucket 140 hits an obstacle such as the ground when the cylinder is extended or the boom is lowered, the pressure oil on the bottom chamber 40b side is caused to flow out to the rod chamber 40a side to prevent the cylinder from buckling. . The pressure oil on the bottom chamber 40 b side flows into the cylinder rod chamber 40 a via the check valve 5 b built in the sequence valve 5 and the check valve 3 b built in the counter balance valve 3. As a result, the rod chamber 40a and the bottom chamber 40b have the same pressure, and their thrusts are offset. That is, if the pressure receiving area ratio between the rod chamber 40a and the bottom chamber 40b is, for example, 1: 1.98, the cylinder thrust can be suppressed to about half of the total thrust due to the pressure on the bottom chamber 40b side, and the cylinder buckling Can be prevented.
[0038]
When the pressure in the bottom chamber 40b further rises and reaches the set pressure of the overload relief valve 9, the overload relief valve 9 opens and the pressure oil flows out to the control valve 20 side. It is led to the tank through the valve 20. At this time, since the operation pedal 21 is operated to the extension side (or in a non-operation state), the direction switching valve 14 is in the position (a). Therefore, the pipe line 12 communicates with the tank 22, and the pressure oil that has flowed to the control valve 20 side through the overload relief valve 9 is also guided to the tank 22 by the pipe line 12 and the direction switching valve 14.
[0039]
(4) When pulling out the arm
To pull out the adsorbed clamshell bucket 140, the telescopic arm 120 or the boom 110 is used. Here, a case where the clamshell bucket 140 is pulled out using the telescopic arm 120 will be described.
[0040]
After pressing the clamshell bucket 140 against the ground and scooping the earth and sand, the operator operates the operation pedal 21 to the contraction side. Thereby, the control valve 20 is switched to the position (b), and the pressure oil discharged from the pump 10 flows into the rod chamber 40a of the telescopic cylinder 40 through the rod side conduit 16 for contraction. While the clamshell bucket 140 is adsorbed to the ground, the telescopic cylinder 40 is not expanded and contracted, so that the region surrounded by the rod chamber 40a, the counter balance valve 3 and the check valve 8 continues to be pressurized.
[0041]
However, when the pressure of the pilot pressure oil in the pilot lines 1 and 2 reaches the set pressure A3 of the counter balance valve 3, the counter balance valve 3 is opened. Along with this, the sequence valve 5 set at a lower set pressure than the counter balance valve 3 is also opened, so that the pressure oil on the rod chamber 40a side flows out to the bottom chamber 40b side through the short circuit 31, The circuit can be protected.
[0042]
(5) When the arm contracts
As in the case of pulling out the arm, when the operation pedal 21 is operated to the contraction side in order to pull up the clamshell bucket 140, the control valve 20 is switched to the position (b), and the pressure oil discharged from the main pump 10 contracts. It flows into the rod chamber 40a side of the telescopic cylinder 40 through the rod side conduit 16 for use. The pressure oil from the pump 10 is also led to the pilot lines 6 and 7 from the pilot line port 34 provided on the control valve 20 side than the check valve 8, and the counter balance valve 3 and the sequence valve 5 are respectively moved together with the spring force. It works so as not to open the valve. Therefore, the pressure oil that has passed through the check valve 8 provided in the rod side pipe line 16 is reliably supplied to the rod chamber 40 a and contracts the telescopic cylinder 40.
[0043]
At this time, since the operation pedal 21 is operated to the contraction side, the pilot pressure oil is also supplied to the direction switching valve 14 through the pipeline 11. By this pilot pressure oil, the direction switching valve 14 is switched to the position (b) against the spring force. The conduit 12 that connects the rod side conduit 16 and the tank 22 is blocked, and the conduit 13 communicates with the tank 22. Therefore, the pressure oil discharged from the bottom chamber 40b when the telescopic cylinder 40 contracts returns to the tank through the conduit 13 and the direction switching valve 14. Further, the pressure oil discharged from the bottom chamber 40 b returns to the tank 22 through the bottom side pipe line 15 and the control valve 20. In this way, by providing the pipeline 13 and the pipeline 15 on the bottom chamber 40b side to make two systems, the flow rate of the return pressure oil flowing out from the bottom chamber 40b to the tank 22 when the expansion cylinder 40 contracts, Back pressure can be reduced. As a result, the speed at which the telescopic cylinder 40 contracts increases.
[0044]
In addition, the hydraulic circuit of the multistage telescopic arm according to the present invention is not limited to the above embodiment, and various modifications can be made. In the above-described embodiment, the counter balance valve 3 and the sequence valve 5 each have built-in check valves 3b and 5b. However, these may not be built in, and for example, a check valve that allows the flow of pressure oil from the bottom chamber 40b side to the rod chamber 40a side may be provided on the expansion cylinder 40 side of the short circuit 31. Further, the telescopic arm 120 may not have a three-stage configuration as long as it has a plurality of stages.
[0045]
If the counter balance valve 3 can be opened and closed accurately by the pilot pressure oil from the pilot pipelines 1 and 2 and does not cause the hunting phenomenon, it is not necessary to provide the throttle 4 or the sequence valve 5 that functions as a throttle. Good. A drain circuit communicating with the pilot line 6 or the rod side line 16 may be provided in the pilot line 2 to reduce hunting by the counter balance valve 3.
[0046]
As described above, the hydraulic circuit of the multistage telescopic arm according to the embodiment of the present invention includes the counter balance valve 3 and the sequence valve in which the return pressure oil from the rod chamber 40a is provided in the short circuit line 31 when the telescopic cylinder 40 is extended. 5 and flows into the bottom chamber 40b, the extension speed of the arm 120 can be increased. Further, since the counter balance valve 3 is an internal / external pilot combined type counter balance valve using the pilot pipelines 1 and 2, the counter balance valve 3 is opened at a relatively low pressure. As a result, since the operating pressure when the telescopic cylinder 40 is extended can be kept low, the flow rate can be increased by joining two pumps, and the extension speed can be further increased.
[0047]
When the arm is pushed in, the return oil from the bottom chamber 40b flows into the rod chamber 40a through the check valves 5b and 3b, and the rod chamber 40a and the bottom chamber 40b of the expansion cylinder 40 are made to have the same pressure. Buckling can be prevented.
[0048]
Furthermore, the return circuit on the bottom chamber 40b side is divided into two systems, and the return oil from the bottom chamber 40b passes through the two pipe lines 13 and 15 to the tank 22, so the influence of the back pressure when the expansion cylinder 40 contracts. And the contraction speed of the arm 120 can be increased.
[0049]
If the counter balance valve 3 and the sequence valve 5 are replaceable cartridge valves, the maintenance performance of the regeneration valve unit 30 can be improved.
[0050]
In the correspondence between the embodiment described above and the claims, the pipe 12 is the rod side branch pipe, the pipe 13 is the bottom side additional pipe, the check valve 8 is the first check valve, and the check valve 3b. , 5b correspond to the second check valves, respectively.
[0051]
【The invention's effect】
As described above, the hydraulic circuit of the multistage telescopic arm according to the present invention is connected from the hydraulic pump side to the rod side pipe line that connects the hydraulic pump that drives the hydraulic cylinder for extending and retracting the multistage telescopic arm and the rod chamber of the hydraulic cylinder. A first check valve that allows the flow of pressure oil to the rod chamber side and prohibits the flow of pressure oil from the rod chamber side to the hydraulic pump side is provided, and the counter balance between the rod chamber and bottom chamber of the hydraulic cylinder is provided. Communication was made by a short circuit provided with a valve. Thus, the pressure oil discharged from the rod chamber when the hydraulic cylinder is extended can surely flow into the bottom chamber without flowing out to the control valve side, and the hydraulic cylinder extension speed can be increased.
[Brief description of the drawings]
FIG. 1 is an overall view of a hydraulic excavator equipped with a hydraulic circuit of a multistage telescopic arm according to the present invention.
FIG. 2 is a side view of a multistage telescopic arm according to an embodiment of the present invention.
FIG. 3 is a hydraulic circuit diagram of the multistage telescopic arm shown in FIG.
FIG. 4 is a schematic view of a counter balance valve 3
[Explanation of symbols]
1, 2, 6, 7, 11: Pilot pipeline
3: Counter balance valve
5: Sequence valve
8: Check valve
9: Overload relief valve
14: Directional switching valve
20: Control valve
30: Regenerative valve unit
40: Arm telescopic cylinder
40a: Rod chamber
40b: bottom chamber
101: Lower traveling body
102: Upper swing body
110: Boom
120: Telescopic arm
140: clamshell bucket

Claims (7)

A hydraulic cylinder driven by pressure oil discharged from a hydraulic pump and extending and retracting a multistage telescopic arm of a telescopic clamshell;
Pressure oil provided in a rod side conduit that communicates the rod chamber of the hydraulic cylinder and the hydraulic pump, allowing pressure oil discharged from the hydraulic pump to flow into the rod chamber, and from the rod chamber A first check valve that prohibits the oil from flowing out to the hydraulic pump side;
A short circuit that communicates the rod chamber and the bottom chamber of the hydraulic cylinder via a counterbalance valve;
An inlet on the rod chamber side of the short circuit is provided in the rod side pipe line between the rod chamber and the first check valve, and the counter balance valve is at least a pilot from the rod chamber side. Open according to pressure ,
A second check valve that allows the flow of pressure oil from the bottom chamber to the rod chamber and prohibits the flow of pressure oil from the rod chamber to the bottom chamber;
The outlet side port of the second check valve, the hydraulic circuit of the multistage telescopic arm to which is connected to the rod side conduit wherein Rukoto between said rod-side port of the first check valve. In the hydraulic circuit of the multistage telescopic arm according to claim 1,
The hydraulic circuit of a multistage telescopic arm, wherein the counter balance valve opens in response to pilot pressure from the rod chamber side and the bottom chamber side. In the hydraulic circuit of the multistage telescopic arm according to claim 1,
A pilot line for supplying the counter balance valve with pilot pressure oil acting in a direction to close the counter balance valve when the hydraulic cylinder is contracted;
A hydraulic circuit for a multistage telescopic arm, wherein an inlet of the pilot pipeline is provided in the rod side pipeline closer to the hydraulic pump than the first check valve. In the hydraulic circuit of the multistage telescopic arm according to any one of claims 1 to 3,
The hydraulic circuit of the multistage telescopic arm, wherein the second check valve is built in the counter balance valve . In the hydraulic circuit of the multistage telescopic arm according to any one of claims 1 to 4 ,
A rod side branch pipe extending from the rod side pipe to communicate the rod chamber of the hydraulic cylinder and the tank;
A bottom-side additional conduit for communicating the bottom chamber of the hydraulic cylinder with the tank;
A directional switching valve that switches either one of the rod side branch pipe and the bottom side additional pipe to communicate with the tank;
The direction switching valve communicates the rod-side branch conduit with the tank when the hydraulic cylinder is extended and stopped, and shuts off the bottom-side additional conduit from the tank, and when the hydraulic cylinder is contracted, the bottom side additional conduit through the tank and communicating, the hydraulic circuit of the multistage telescopic arm the rod-side branch line, characterized that you cut off from the tank. In the hydraulic circuit of the multistage telescopic arm according to claim 1 ,
It said counter to said short circuit on the outlet side of the balance valve, the hydraulic circuit of the multistage telescopic arm, characterized in Rukoto provided sequence valve. The multistage telescopic arm is attached to a boom provided on a telescopic clamshell work machine body on which the hydraulic circuit of the multistage telescopic arm according to any one of claims 1 to 6 is mounted, and is attached to a tip of the multistage telescopic arm. A telescopic clamshell working machine with a clamshell bucket attached .

Images